Albumin is the main protein synthesized by the normal adult liver and it is secreted into the blood where it acts not only to maintain the osmotic pressure of the body fluids but also to carry various compounds such as essential metabolites, hormones, drugs and inorganic ions. Some liver tumors, termed hepatomas, are capable of producing albumin, but they generally do so at a reduced level. In addition, it has been proposed by some investigators that some rat liver transplantable hepatomas (Morris hepatoma 5123C for example) are incapable of secreting albumin into the bloodstream. In order to understand the pathological conditions in these hepatomas which make them apparently unable to secrete albumin, a comparative study of the biosynthesis and secretion of albumin by normal liver and by two transplantable hepatomas (5123C and 7800) was undertaken. It was found that these hepatomas, like rat liver, appear to be able to transport and process newly made albumin within the cell in a normal fashion and that slices prepared from these tissues are capable of secreting the newly made albumin into the incubation flasks. Why these hepatomas appear to act differently in vitro than they do in the animal will be the subject of further experimentation.